1. Field of the Invention
The present invention relates to an .alpha.-olefin polymerization catalyst and a process for producing an .alpha.-olefin polymer. Particularly, the present invention relates to a catalyst having extremely high catalytic activity and giving an .alpha.-olefin polymer having an extremely high stereoregularity, and a process for producing an .alpha.-olefin polymer with said catalyst.
2. Prior Art
As a process for producing a polymer of .alpha.-olefin such as propylene, butene-1 and the like, it is well known that the so-called Ziegler-Natta catalyst comprising the transition metal compound of the 4th to 6th Groups in the Periodic Table and the organometallic compound of the 1st, 2nd and 13th Groups is used. In the production of an .alpha.-olefin polymer, an amorphous polymer is produced as a by-product in addition to a high stereo-regular .alpha.-olefin polymer having a high value for an industrial application. This amorphous polymer has a little value for an industrial application and effects largely a bad influence on mechanical properties, when the .alpha.-olefin polymer is molded to a molded article, a film, a fiber and other fabricated goods to be used. Besides, the formation of an amorphous polymer causes the loss of a raw material monomer and at the same time, an apparatus for removing the amorphous polymer becomes necessary to cause an extremely large disadvantage from an industrial viewpoint. Therefore, it is necessary that a catalyst for producing an .alpha.-olefin polymer produces no amorphous polymer or produces rarely little. Further, in an .alpha.-olefin polymer obtained, a catalyst residue comprising a transition metal compound and an organometallic compound remains. As this catalyst residue causes problems in the various points of the stability, processability and the like of the .alpha.-olefin polymer, an apparatus for removing the catalyst residue and stabilizing the .alpha.-olefin polymer becomes necessary. This drawback can be improved by enlarging a catalyst activity represented by the weight of an .alpha.-olefin polymer produced per the unit weight of a catalyst, the above-mentioned apparatus for removing the catalyst residue becomes unnecessary and the reduction of the manufacturing cost of .alpha.-olefin polymer also becomes possible.
By using a supporting type solid catalyst obtained by treating a magnesium halogenide with an organic ester compound and supporting a tetra-valent titanium halogenide on the treated magnesium halogenide, or a solid catalyst obtained by treating diethoxymagnesium which has Mg--O bonds with phthaloyl dichloride and titanium tetrachloride, the organoaluminum compound of a promotor and the organosilicon compound of the third component of polymerization in combination, it is known that a certain measure of the highly stereo-regular and highly active polymerization of .alpha.-olefin can be realized. (Japanese Patent Publication (Unexamined) sho Nos. 57-63310, 58-83006 and 61-78803, and Japanese Patent Publication (unexamined) No. Hei No.4-8709) It is known that the highly stereo-regular and highly active polymerization of .alpha.-olefin can be realized to a certain extent by a similar combination in a Ti--Mg complex type solid catalyst obtained by reducing a tetra-valent titanium compound by an organomagnesium compound in the coexistence of an organosilicon compound and forming a magnesium-titanium eutectic mixture. (Japanese Patent Publication (Examined) Hei Nos.3-43283 and 1-319508)
Furthermore, by using dicyclopentyldimethoxysilane as the organosilicon compound of the third component of in a catalyst system, a supporting type solid catalyst obtained by supporting a tetra-valent titanium halogenide on a magnesium halogenide, and the organoaluminum compound as co-catalyst component in combination, it is known that a certain measure of the highly stereo-regular and highly active polymerization of .alpha.-olefin can be realized. (Japanese Patent Publication (Unexamined) Hei No.2-84404) In any case, a non-extraction and non-deashing process is in a possible level but furthermore, a more improvement is desired. In the concrete, in order to make an .alpha.-olefin polymer having high quality, the realization of a further highly stereo-regular polymerization is desired. Particularly, in a use such as a field for molding wherein it is desired to make a polymer having high rigidity, a highly stereo-regular polymer brings directly out the quality of a high rigidity and therefore, the appearance of a catalyst having a further highly stereoregular polymerizability is acutely desired.